In the prior art toe positioning unit of a treadle of a bicycle, the treadle is formed with a front clamper and a rear clamper for providing elastic forces to the treadle so as to position the toe positioning unit. When the toe of the user desires to separate from the treadle, the movement of the leg will make the front clamper and the rear clamper to separate from the toe positioning unit so that the toes can leave from the treadle.
However, in driving, the movement of the leg will make the toe positioning unit separating from the treadle, but this is not a desired result.
In another design, a spring is further attached to the treadle. The tightening or releasing of the spring will change the tightness of the front clamper and rear clamper to the treadle.
However, above mentioned spring can still not change the problem that the toe positioning unit separate from the treadle due to normal movement of the leg in driving the bicycle.
Moreover, the adjustment of the spring is not suitable for users because of the applying force of the user and the treading habit of the user.